Elevated atmospheric CO(2) concentration changes ectomycorrhizal morphotype assemblages in Betula papyrifera.

Ectomycorrhizae are extremely diverse, with different species of fungi having very different physiologies and morphologies that, in turn, confer a range of different benefits to the host plant. To test the hypothesis that elevated CO(2) leads to changes in the assemblage of ectomycorrhizae associated with trees, we examined the number and frequency of ectomycorrhizal morphotypes colonizing roots of Betula papyrifera Marsh. saplings grown at an ambient or elevated (700 ppm) atmospheric CO(2) concentration for 24 weeks. Elevated CO(2) resulted in significant changes in the composition of the ectomycorrhizal assemblage toward morphotypes with a higher incidence of emanating hyphae and rhizomorphs. We conclude that B. papyrifera saplings will be able to support a more costly mycorrhization in future elevated-CO(2) atmospheres.